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Deployment

Last updated: 10 Mar 2021

Fall back to AWS CloudFront

There is a backup Content Delivery Network (CDN) that can be used if Fastly is down. This backup CDN is currently provided by AWS CloudFront.

Important At the time of writing, GOV.UK will be served by static mirrors and not the origin of GOV.UK if you fallback to the backup CDN.

Procedure

You will have to make 2 DNS changes to GOV.UK:

  1. The CNAME at www-cdn.production.govuk.service.gov.uk should point to cloudfront’s WWW distribution instead of Fastly
  2. The CNAME at assets.publishing.service.gov.uk should point to cloudfront’s Assets distribution instead of Fastly

This Draft PR to Failover to AWS CloudFront shows the changes you need to make, and how to test the CDN before failing over.

You can check the domain names of the cloudfront distributions by looking in the AWS web console, or with the CLI:

# www.gov.uk
gds aws govuk-production-readonly aws cloudfront list-distributions --query "DistributionList.Items[?Comment=='WWW'].DomainName | [0]"

# assets.publishing.service.gov.uk
gds aws govuk-production-readonly aws cloudfront list-distributions --query "DistributionList.Items[?Comment=='Assets'].DomainName | [0]"

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